How to Determine Whether Humans Are More Closely Related to Cats or Dogs

Introduction

If you have ever wondered whether you share more evolutionary history with your cat or your dog, you are not alone. The question seems simple, but the answer depends entirely on how you define “relatedness.” This step-by-step guide will walk you through the scientific and practical factors that influence the answer. By the end, you will know how to evaluate the evidence for yourself and understand why the question is more subtle than it appears.

What You Need

Before you begin, gather these prerequisites:

• A basic understanding of evolutionary biology (common ancestry, divergence times)
• Curiosity about genetics and behavior
• Access to online resources or a biology textbook (optional, for deeper dives)
• A willingness to consider multiple perspectives

Step 1: Clarify the Question – What Does “Related” Mean?

The first and most important step is to define your terms. “Related” can mean:

• Genetic relatedness – the percentage of DNA shared or the time since the last common ancestor.
• Evolutionary relatedness – how close the species are on the tree of life.
• Behavioral or emotional relatedness – the bond we feel, or how similarly we behave.
• Historical co‑evolution – how long we have lived alongside each species.

Write down which interpretation you are most interested in. This will guide your investigation.

Step 2: Explore the Evolutionary Tree of Mammals

To judge genetic and evolutionary relatedness, you need to look at the family tree. Humans belong to the order Primates, while cats and dogs are both in the order Carnivora. The split between primates and carnivorans happened about 80–90 million years ago – long before cats and dogs parted ways.

Within Carnivora, the cat lineage (Feliformia) and dog lineage (Caniformia) diverged roughly 55 million years ago. This means that humans are equally distant from both cats and dogs when considering the primate–carnivore divergence. Both cats and dogs are about 80–90 million years removed from us, while they are only 55 million years from each other.

Step 3: Compare Genetic Similarities

Now look at the molecular data. Genomic studies show that humans share approximately 90% of their DNA with both cats and dogs. The actual percentage varies slightly depending on which gene regions are compared, but the difference is negligible. For example:

• Human–cat genome similarity: about 90%
• Human–dog genome similarity: about 85–90% (depending on the study)

However, a more accurate measure is the number of genetic differences since the last common ancestor. Both cats and dogs are equally divergent from humans because the primate–carnivoran split predates the cat–dog split. Therefore, on a strict genetic level, we are equally related to both.

Step 4: Consider Behavioral and Historical Perspectives

This is where the “depends on how you look at it” part becomes real. While genetics says we are equally related, other measures tip the scale:

• Co‑evolution with dogs: Dogs were domesticated at least 15,000 years ago, likely earlier. This long partnership has shaped human society and even our own evolutionary path (e.g., changes in digestion, social behavior).
• Behavioral similarities: Dogs and humans both evolved in complex social groups. Dogs understand pointing, gaze following, and some verbal commands in a way that cats generally do not.
• Cats’ independent nature: Cats were domesticated more recently (about 8,000–10,000 years ago) and retain more solitary, self‑reliant traits. Their behavior is less similar to ours in terms of social hierarchy and communication.

So if “related” means shared social behaviors or a long history of mutual influence, you might say humans are more closely related to dogs.

Step 5: Synthesize and Draw Your Conclusion

Now bring together all the evidence:

• Genetically and evolutionarily: Humans are equally related to cats and dogs. The point of divergence from our primate ancestors is the same for both.
• Behaviorally and historically: Dogs are often considered closer because of our prolonged co‑evolution and similar social structure.
• Perceived closeness: Many people feel a stronger bond with dogs, but that is subjective.

Your final answer will depend on which criteria matter most to you. The key is to understand that “related” can be measured in multiple ways.

Tips for a Complete Understanding

• Tip 1: Remember that genetic relatedness is objective, while emotional connection is personal. Both are valid, but they answer different questions.
• Tip 2: Use online tools like the NCBI Taxonomy Browser or TimeTree to visualize divergence times.
• Tip 3: When reading popular science articles, check whether they are discussing genetic, evolutionary, or behavioral relatedness – they often mix terms.
• Tip 4: Teach this process to a friend or child. Explaining the difference between the two perspectives will deepen your own understanding.
• Tip 5: Be open to ambiguity. Science doesn’t always give a single neat answer, and that’s okay.